It has long been known to prepare coupled polymers by polymerizing conjugated dienes and/or monovinylarenes in the presence of an organomonolithium initiator to produce polymer containing an active lithium atom on one end of the polymer chain (such a polymer called polymer lithium and often referred to as living polymer). Coupled polymers are formed by reacting the polymer lithium with a coupling agent (i.e., a compound capable of reacting with at least two polymer lithiums).
A wide variety of coupling agents are known including esters, diesters, and polyesters. However, there are no known reports in the art of any coupling agent being specific to monovinylarenyllithium-terminated living polymers and essentially not coupling conjugated dienyllithium-terminated living polymers. A monovinylarenyllithium-terminated living polymer is defined to be a living polymer in which the lithium atom is attached to a terminal monovinylarenyl group in a polymer molecule.
An object of this invention is to couple polymer lithiums.
Another object of this invention is to produce coupled polymers.
Yet another object of this invention is to selectively couple particular polymer lithiums.
A further object of this invention is to couple homopolymers formed from monovinylarene monomers and to couple copolymers comprising polymerized conjugated diene monomers and monovinylarene monomers.
A still further object of this invention is to couple monovinylarenyllithium-terminated living homopolymers and copolymers.
It is also an object of this invention to couple monovinylarenyllithium-terminated living polymers selectively, under conditions wherein conjugated dienyllithium-terminated living polymers are essentially not coupled.